The purpose of this project is to construct up-to-date genetic maps of the human chromosomes, and to test hypotheses concerning the chiasma map, interference, race and sex differences, and disease heterogeneity. To do this, all published human linkage data will be synthesized, and after thorough checking, this linkage data set will be available to researchers. Two books, "A Source Book for Linkage in Man" and "Linkage and Chromosome Mapping in Man", containing linkage information from 2,421 articles available to the end of 1980, have already been published by the Principal Investigator; they are very useful references for researchers in the linkage field, as well as for clinical geneticists and genetic counselors who need information on linkage of diseases with other markers. It is essential that the chromosome maps and the data set used to construct them be kept up to date, and be readily accessible as a secure base for formal genetics and genetic counseling. Using maximum likelihood methods, genetic maps of each of the chromosomes will be constructed; pairwise lod score data from family studies will be used, and the extra information obtained by including n-point data, physical locations of markers, and the chiasma map estimated from the observed distribution of chiasmata in spermatocytes will be determined. Lod score, recombinant count, and regional assignment information from new publications will be synthesized, as well as the results we obtain from linkage analyses of our own pedigree data. The new data will include results from the analysis of restriction fragment length polymorphisms (RFLPs). All applications of linkage to antenatal diagnosis and genetic counseling depend on the frequency with which linked genes are transmitted together to progeny. Precise chromosome maps based on recombination rates are required for determining these transmission probabilities; they cannot be inferred from physical distances. Thus, accurate recombination maps based on up-to-date lod score information are essential for applying linkage to genetic counseling.